function verDiv(){
    var div = document.getElementById("logear");
    div.setAttribute("class", "visible");
    div=document.getElementById("ventana");
    div.setAttribute("class", "visible");
    document.getElementById("usuario").focus();
}

function quitarDiv(){
    var div = document.getElementById("logear");
    div.setAttribute("class", "noVisible");
    div=document.getElementById("ventana");
    div.setAttribute("class", "noVisible");
}